A necessary and sufficient condition to rule out arbitrage profits in the single-period HJM binomial tree is that the following must hold O a. "up factor > down factor > dollar return" [U>D> (1 + R)] for all zero-coupon bonds Ob U>(1 + R) > D for all zero-coupon bonds O c. the risk-neutral probabilities must be equal for all zero-coupon bond/money market account pairs Od the risk-neutral probabilities must be equal to 1/2. Oe. None of given answers is correct